1. Field of the Invention
The present invention relates to gas extraction devices for molds and, particularly, to a gas extraction method for a plastic molding mold capable of sufficiently removing air and reaction product gases from a cavity of a mold.
2. Description of Related Art
Most products made of polymers or other plastics are typically created using injection molds. During a typical injection molding process, a molten material is injected into a mold cavity via a runner. The molten material in the cavity is cooled to form the molded product.
However, the molten material usually contains air or reaction product gases. If the gas in the cavity is not extracted, the gas might affect the formation of the final product. In a conventional injection mold apparatus, a means of extracting gas uses a plurality of venting holes defined at a parting plane between two separable sections of the injection mold. Alternatively, the gas is exhausted through a gap between an ejector pin and an ejector pin hole. However, these conventional venting methods create surface burrs on the molded product.
Therefore, an improved gas extraction method is desired in order to overcome the above-described problems.